GASTEROPODA. 101 



Genus 20.— EM ARGll^Uh A.— Lamarck. 



Generic Character. — Body of the animal creeping ; having 

 two conical tentacula, with the eyes placed at their. external 

 base ; mantle large, partly covering the margin of the shell ; 

 foot large and thick. — Shell conical, shield-shaped; vertex in- 

 clined to one side ; internal cavity simple ; the dorsal margin 

 with a fissure. 



Emarginulajissura.— The Slit Emarginula. Plate XIV. 

 fig. 17. Oval, with reticulated striae, and ribs radiating from the 

 vertex, which is obtuse and slightly recurved ; margin with a fis- 

 sure, which extends nearly half-way to the vertex ; inside glossy 

 white. Three- eighths of an inch long. Inhabits the British 

 seas. 



Genus 21.— PARMOPHORUS.— ZawiarcyJ. 



Generic Character. — Body creeping, very thick, oblong-ovate, 

 broad behind, obtuse at the extremities ; border of the mantle 

 cleft before, and suspended vertically around ; back shell shield- 

 shaped, and partly covered ; head distinct, and slit below ; two 

 conical contracted tentacula, at the base of which are placed 

 the eyes, which are somewhat pedunculated ; mouth below, 

 funnel-shaped, oblique, truncated and concealed; branchial 

 cavity opening anteriorly behind the head by transverse fissure. 

 — Shell oblong, somewhat in the form of a parallelepiped ; 

 slightly convex above, with a small sinus before ; apex pointed, 

 inclined backwards. 



Parmophorus Australis — The Australian Parmophorus. 

 Plate XIV. fig. 22. Shell oblong, depressed; vertex slightly 

 recurved ; concentrically striated ; the posterior margin rounded, 

 and the anterior truncated. Two inches long. Inhabits the 

 Australian coasts. 



TRIBE V. SEMIPHYLLIDIACEA. 



Branchiae situated under the margin of the mantle, and set 

 in a longitudinal series, on the right side of the body. The 

 animals respire under water, 



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